This invention relates to a process for producing high concentration oxygen by a pressure-swing-adsorption method (hereinunder referred to as a PSA method) using air as a raw material.
In a conventional process for producing oxygen by a PSA method using air as a raw material, air is subjected to adsorption by a zeolite molecular sieve having small pore diameters of 5.ANG. or thereabout which is packed in two or more adsorption columns, under an atmospheric or higher pressure and then desorption is made under a pressure lower than an atmospheric pressure, to obtain oxygen of up to 95% concentration.
In this case, the zeolite molecular sieve having small pore diameters of 5.ANG. or thereabout characteristically adsorbs nitrogen in preference to oxygen and argon. However, even if an assumption is made that nitrogen can be completely adsorbed and as a result the concentrations of oxygen and argon can be increased from 20.9% and 0.9% in air, respectively to maximum about 5 times said values, respectively, the concentration of oxygen can not be increased to higher than about 95% because of the copresence of about 5% of argon. In fact, there is known no process for producing oxygen of a concentration higher than 95% by a PSA method.